KR20210083270A - Porous metal foil or wire and capacitor anode made therefrom and method for manufacturing the same - Google Patents

Abstract

Porous metal foils and porous metal wires are described. Further described are capacitor anodes made of either or both of a porous metal foil and a porous metal wire, as well as a method of making the same.

Description

Porous metal foil or wire and capacitor anode made therefrom and method for manufacturing the same

This application is filed on October 30, 2018 in the preceding U.S. 35 U.S.C. of Provisional Patent Application No. 62/752,431. Claims benefit under §119(e), the provisional patent application is hereby incorporated by reference in its entirety.

FIELD OF THE INVENTION The present invention relates to metal foils and wires and to anodes and capacitors carrying them. In particular, the present invention relates to a porous metal foil or wire comprising a tantalum foil.

The present invention further relates to a method for manufacturing a porous metal foil or wire, as well as a method for manufacturing an anode and a capacitor comprising a porous metal foil.

Valve metal powders, such as tantalum powder, are commonly used to make capacitor electrodes, among their many applications.

Currently, for example, tantalum powder is generally produced via one of two methods: a mechanical process or a chemical process. The mechanical process includes electron beam melting of tantalum to form an ingot, hydrogenating the ingot, crushing the hydride, followed by dehydrogenation, crushing, and thermal treatment. Powders with high purity are generally produced by this process.

Another commonly used process for making tantalum powder is a chemical process. Several chemical methods for preparing tantalum powder are known in the art. US Pat. No. 4,067,736, issued to Vartanian, and US Pat. No. 4,149,876, issued to Rerat, describe a chemical manufacturing process involving sodium reduction of _{potassium fluorotantalate (K 2} TaF _{7 ).} it's about Exemplary techniques are also reviewed in the background section of US Pat. No. 4,684,399 to Bergman et al. and US Pat. No. 5,234,491 to Chang. All patents and publications are incorporated herein by reference in their entirety.

For example, tantalum powder produced by chemical methods is well suited for use in capacitors because it generally has a larger surface area than powders produced by mechanical methods. Chemical methods generally include chemical reduction of tantalum compounds using a reducing agent. Typical reducing agents include hydrogen and active metals such as sodium, potassium, magnesium and calcium. Typical tantalum compounds are potassium fluorotantalate _{(K 2 TaF 7} ), sodium _{fluorotantalate (Na 2} TaF ₇ ), tantalum pentachloride (TaCl ₅ ), tantalum pentafluoride _{(TaF 5} ) and its mixtures, but are not limited thereto. The most common chemical process is the reduction of _{K 2} TaF _{7 using liquid sodium.}

In the case of chemical reduction of valve metal powder, such as tantalum powder, potassium fluorotantalate is recovered, melted and reduced via sodium reduction to obtain tantalum metal powder. The dried tantalum powder may then be recovered and thermally agglomerated optionally under vacuum to avoid oxidation of the tantalum and to crush it. The granular powder is then typically mixed with a getter material, such as an alkaline earth metal (e.g., magnesium), which has a higher oxygen affinity than the valve metal, as the oxygen concentration of the valve metal material may be important in the manufacture of the capacitor. ) at elevated temperatures (eg, up to about 1000° C. or greater). Prior to further processing of the material, normal atmospheric conditions (e.g., using an inorganic acid solution comprising, for example, sulfuric or nitric acid) to dissolve metal and refractory oxide contaminants (e.g., magnesium and magnesium oxide contaminants) For example, acid leaching may be performed after a deoxidation process carried out under approximately 760 mm Hg). The acid leached powder may be washed and dried, then compressed, sintered and anodeized in a conventional manner to produce sintered porous masses, such as anodes for capacitors.

Most of the effort in the development of tantalum powder was driven by the capacitor anode industry, where the powder was prepared for this specific purpose only.

As technology advances and electrical devices become smaller and smaller, there is a desire to provide an anode that can be used in such small or miniature devices. Many anodes today, as described above, take tantalum powder, press the powder into an anode mold and sinter the anode to form a sintered body, which is then anodeized in an electrolyte to form a dielectric oxide film on the sintered body and ultimately a capacitor By forming an anode, it is prepared. A method of pressing and sintering using starting tantalum powder creates difficulties because the anode can only be made that small. Therefore, it is generally understood that it is extremely difficult to obtain acceptable anodes thinner than 0.2 mm by using traditional pressing and sintering methods.

Accordingly, there is a need in the industry to provide an acceptable anode that can have a consistently thin thickness to form an anode thinner than 0.2 mm in thickness.

It is a feature of the present invention to provide a porous metal foil or wire that can be used to form thin capacitor anodes.

Another feature of the present invention is to provide an anode and a capacitor made of a porous metal foil or wire.

It is a further feature of the present invention to provide a method of forming a porous metal foil or wire that can be used in the manufacture of an anode.

Additional features and advantages of the invention will be set forth in part in the description that follows, and in part will become apparent from the description or may be learned by practice of the invention. The objects and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the description and appended claims.

To achieve these and other advantages, for the purposes of the present invention, as embodied and broadly described herein, the present invention relates in part to a porous metal foil or wire. The porous metal foil or wire has a thickness and an outer surface. The porous metal foil or porous metal wire consists of or comprises or is a tantalum foil having a nominal thickness of 0.2 mm or less or a diameter of from about 0.05 mm to about 1.0 mm. The porous metal foil or porous metal wire further has pores at least on the outer surface of the metal foil or metal wire.

The invention further relates to a capacitor anode comprising or formed from the porous metal foil of the invention and a dielectric oxide film formed on the porous metal foil.

The present invention also relates to a method of forming the porous foil or wire of the present invention comprising subjecting a metal foil or wire composed of or comprising tantalum to an oxidation treatment to form an oxide layer on the metal foil or wire. . The method further comprises then subjecting the metal foil or wire to a deoxidation treatment to form pores on at least the surface of the metal foil or wire.

It should be understood that both the foregoing general description and the following detailed description are exemplary and descriptive only and are intended to provide a further description of the invention as claimed.

[Figure 1] Figure 1 is an SEM photograph of the foil and wire formed in the present invention, and shows an existing porous structure. In particular, the etched surface can be seen, similar to the particle-like exposed surface, as shown in the SEM picture.
[Figure 2] Figure 2 is a flow chart showing an example of a process that can be used in the present invention.

The present invention relates to a porous metal foil or porous metal wire. Further, the present invention relates to a capacitor anode comprising or formed from a porous metal foil and/or a porous metal wire. Additionally, the present invention relates to a method of forming the porous metal foil or porous metal wire of the present invention. The invention further relates to another aspect as described herein.

More specifically, the porous metal foil or porous metal wire of the present invention has a thickness and an outer surface (ie, an outer surface or an exposed surface). The porous metal foil comprises, consists of, consists essentially of, consists of, or is a tantalum foil having a nominal thickness. This thickness may be, for example, 0.2 mm or less. Additionally, the porous metal foil has pores on at least the outer surface.

Regarding the thickness of the metal foil or the thickness of the tantalum foil, as described, this thickness may be 0.2 mm or less or other thicknesses. For example, the thickness may be from 0.01 mm to 0.2 mm, or from 0.02 mm to 0.2 mm, or from 0.012 mm to 0.2 mm, or from 0.025 mm to 0.15 mm, or from 0.05 mm to 0.1 mm, or from 0.04 mm to 0.1 mm, or 0.015 mm. to 0.09 mm and other thicknesses within or outside this range.

For the purposes of the present invention, a metal foil may be considered a metal ribbon or metal strip having the thicknesses described herein. For the purposes of the present invention, a tantalum foil may be considered a tantalum ribbon or tantalum strip having the thicknesses described herein. Metallic foils, such as tantalum foils, may be powder-full grade or ingot-derived grade (eg, electron beam (EB) grade). Metal foils such as tantalum foils (or starting metal foils such as starting tantalum foils) are available from Global Advanced Metals USA, Alfa Aesar, H.C. It is commercially available from a number of suppliers including H.C. Starck.

The porous metal foil of the present invention may have a metal purity (excluding gases) that may be at least 99.9% Ta (by weight). Such purity may be, for example, at least 99.95% Ta, or at least 99.99% Ta, or, for example, about 99.9% Ta to 99.995% Ta or more.

Optionally, the porous metal foil can have a carbon content or amount of less than 200 ppm, for example less than 100 ppm, or less than 50 ppm or less than 25 ppm. For example, the amount or content of carbon in the porous metal foil may be from about 5 ppm to about 199 ppm or from about 10 ppm to 175 ppm, or from about 15 ppm to 150 ppm, or from about 25 ppm to 150 ppm of carbon (in elemental form). carbon (in elemental form).

The porous metal foil can have the above-mentioned purity level for tantalum in combination with any one of these carbon content or amount ranges.

The porous metal foil of the present invention further has pores as described herein. These pores are present at least on the outer surface. The pores on the outer surface may be uniform or non-uniform. A pore may be understood to be a plurality of pores and/or pores.

The pores of the metal foil may be present on or on the outer surface as well as optionally subsurface (eg, within the foil or within the foil). Such pores, if present under the outer surface (eg, within the thickness of the porous metal foil), may exist throughout the thickness or through specific regions or portions of the thickness. The pores below the outer surface may be uniform or non-uniform. The depth of any pores present under the outer surface may be even or uneven with respect to the location of the pores from the outer surface. Stated differently, as an example, the pores may be present at a depth of 5 micrometers from the outer surface in some portions of the metal foil but not at the same depth of 5 micrometers in some other portions.

In the present invention, due to the pores formed, the exposed surface has 'islands' of solid metal appearing as main particles or aggregated particles. The exposed surface and particle-like appearance may be considered an etched particulate exposed surface or an etched exposed surface that appears as particles or agglomerated particles. Such etched particulate exposed surfaces can have a size that can be quantified or measured, such as a primary particle size.

Thus, the metal foil or wire may be from about 5 nm to about 500 nm, such as from about 5 nm to about 400 nm, from about 5 nm to about 300 nm, from about 5 nm to about 200 nm, from about 10 nm to about 500 nm; about 20 nm to about 500 nm, about 50 nm to about 500 nm, about 50 nm about 400 nm, about 50 nm to about 300 nm, about 50 nm to about 200 nm, or others within or outside this range It can have a range of particulate (or particle-like) exposure sizes (on exposed surfaces such as those shown in FIG. 1 ). Each of these ranges provided herein may be the average particle size for a particle-like surface present at the exposed surface of the foil or wire.

In the present invention, due to the formation of pores in at least the exposed surface or more than one exposed surface and generally both exposed surfaces (top and bottom surfaces, not the edges of the foil), the surface area on such or all surfaces is the porosity of the present invention. an increase of at least 25%, at least 50%, at least 75%, at least 100%, at least 125% or at least 150% (such as exposure increased surface area by about 25% to 150%). The increase in ^{surface area can be determined by BET (m 2} /g) measurements or other external surface area measurements that measure total surface area.

The porous metal foil of the present invention has pores of 100% by volume or less, 75% by volume or less, 50% by volume or less, 30% by volume or less, 20% by volume or less, such as about 1% by volume to about 1% by volume, based on the total volume of the metal foil. about 100% by volume, about 5% to about 75% by volume, about 5% to about 50% by volume, about 5% to about 30% by volume, about 2% to about 20% by volume, etc. It may have pores present. As noted, with respect to any pores present in these volume percentages, the pores may be uniform or non-uniform when present in the porous metal foil.

In general, the pores of the outer surface, if any, are present in a greater amount (eg, pore number and/or pore density) than any pores below or under the outer surface. For example, the pores on the outer surface can be the same or at least 10% higher in the amount of pores compared to any area below the outer surface. For example, such pores may be at least 20%, at least 50%, at least 75%, at least 100%, at least 20%, at least 50%, at least 75%, at least 100%, at least relative to any area below the exterior surface or inside the metal foil, in the number of pores present on the exterior surface. 150%, at least 200% more. The pores from the surface to the interior may be gradient, wherein the porosity and/or uniformity of the pores decreases from the exterior surface to the interior.

Alternatively and optionally, pores under or inside the outer surface of the metal foil may optionally be present at a level of at least 5 micrometers below the outer surface. For example, such a pore presence level may be at least 10 micrometers under the outer surface, at least 25 micrometers under the outer surface, at least 50 micrometers under the outer surface, or at least 100 micrometers under the outer surface or other depth levels. . Any pores under the outer surface may be uniform or non-uniform and/or may be uniformly present at particular depths or unevenly present at particular depths. For example, strictly as an example, pores may exist at a certain depth in one region of the porous metal foil but not at the same depth in another region. This is particularly an example of non-uniform pores present under the surface. Another example is that the pore density may be the same or different in one area of a certain depth compared to another area of the same depth.

The porous metal foil of the present invention can have any length, any width, and a nominal thickness of generally 0.2 mm or less as described. For example, the length of the metal foil may be from about 10 mm to about 50 mm or other lengths within or outside of this larger or smaller range. The porous metal foil may have a width of from about 5 mm to about 25 mm or other widths within or outside this larger or smaller range.

A porous metal wire having a diameter and an outer surface consists of, comprises, consists essentially of, consists of, or consists of a porous tantalum wire. Such starting metal wires, such as starting tantalum wires for making the wires of the present invention, are commercially available from the same suppliers as the metal foils mentioned herein. With respect to the porous metal wire, the porous metal wire of the present invention has the same characteristics and properties as described herein with respect to the pores for the porous metal foil. What has been discussed herein with respect to the features, properties, and properties in relation to the pores for the metal foil applies equally to this porous metal wire embodiment. What has been discussed with respect to tantalum and its purity in relation to porous metal foils applies equally to porous metal wire embodiments herein, each of which is included in these wire embodiments to avoid repetition.

As described, the porous metal wire of the present invention has an outer surface and has a diameter that can be from about 0.05 mm to about 1.0 mm. This diameter can be from about 0.05 mm to about 0.75 mm or from about 0.05 mm to about 0.5 mm or other diameters within or outside any one of these ranges. The porous metal wire can have any length. The term "diameter" generally refers to a circular cross-sectional shape, but when the cross-sectional shape is a rectangle or other such geometric shape, the term diameter includes such other shapes, in which case the diameter is a parameter of the cross-sectional length and/or width of such other shapes It is understood to represent a variable.

The porous metal foil of the present invention may be used for or formed to be a capacitor anode. The capacitor anode consists of, comprises, consists essentially of, consists of, or is the porous metal foil of the present invention. The capacitor anode further comprises a dielectric oxide film or layer present or formed on the porous metal foil. The porous metal foil forming the capacitor anode may be a sintered porous metal foil.

The invention also relates to a capacitor comprising the capacitor anode of the invention.

The capacitor anode of the present invention may comprise the porous metal wire of the present invention, which may be used in the capacitor anode and/or capacitor of the present invention.

The present invention further relates to a method of forming the porous metal foil and/or porous metal wire of the present invention.

The method of forming a porous metal foil or porous metal wire of the present invention comprises, comprises, or essentially consists of, subjecting the metal foil or wire to an oxidation treatment to form an oxide layer on at least the surface of the metal foil or wire. or may consist of it. The method further includes subjecting the metal foil or wire to a deoxidation treatment after the oxidation treatment to form pores at least on the surface of the metal foil or wire. As described, the pores may be formed on at least one external surface, several external surfaces, or all external surfaces, and may optionally include one or more internal regions or depths below the surface, as described above. Figure 2 shows a summary of these steps.

In the method of the present invention, the step of subjecting the metal foil or wire to oxidation treatment may be repeated one or more times. For example, the oxidation treatment step may be repeated 1, 2, 3, or 1 to 10 or more times. In the case of repetition, the conditions for each step may be the same as or different from the other oxidation treatment steps.

The deoxidation treatment step may be repeated one or more times. For example, this step may be repeated at least 1 time, or at least 2 times, or at least 3 times, or 1 to 10 times or more. The conditions (if repeated) for each deoxidation treatment step may be the same as or different from the previous deoxidation treatment step.

Optionally, the oxidation treatment step and the deoxidation treatment step may each be repeated one or more times.

In the context of an oxidation treatment, this step(s) consists of, comprises, consists essentially of, or consists of calcining the metal foil or wire in air at a temperature that causes oxidation of the metal foil or wire. or it could be that. For example, the temperature may be at least 500°C. The oxidation treatment may be performed for at least 5 minutes or longer, such as 5 minutes to 10 hours or longer. Accordingly, one example of an oxidation treatment is calcining the metal foil or wire in air at a temperature of at least 500° C. for at least 5 minutes. For example, calcination in air may be performed at a temperature of from about 500° C. to about 650° C. for a period of time from about 5 minutes to about 10 hours or longer.

The oxidation treatment(s) may be, include, consist of, consist essentially of, or consist of, a chemical oxidation treatment. One example of a chemical oxidation treatment is the use of an acid such as, for example, HF acid at an elevated temperature (eg, a temperature between 40° C. and 600° C.). The chemical oxidation treatment may be using an alkali bath at an elevated temperature (eg, a temperature of 40°C to 600°C).

In the context of an oxidation treatment for forming an oxide layer on a metal foil or wire, such an oxidation treatment results in a thickness of at least 1 micrometer or a thickness of at least 5 micrometers or a thickness of at least 10 micrometers or a thickness of at least 50 micrometers, etc. An oxide layer having

Optionally, the oxidation treatment reduces oxidation of the foil or wire to 50% or less, 40% or less, 30% or less, 20% or less, or 10% or less by volume relative to the total volume of the metal foil or metal wire. can cause

In the context of a deoxidation treatment, this step consists of, comprises, consists essentially of, or consists of applying a metal foil or wire (as subjected to an oxidation treatment(s)) to the oxygen getter material at an elevated temperature. consists of, or may be. For example, this temperature may be at least 500°C. The time for applying the metal foil or wire to the oxygen getter may be at least 5 minutes. For example, and as an example strictly, the deoxidation treatment may include applying a metal foil or wire to the oxygen getter material at a temperature of at least about 500° C. for a period of time from about 5 minutes to about 10 hours or longer. or it is For example, the temperature may be from about 600°C to 1300°C, or from about 700°C to 1300°C, or from about 700°C to about 1200°C, or from about 700°C to about 1000°C.

Then, after the deoxidation step(s), optionally the metal foil or wire may optionally be subjected to sintering such as vacuum sintering. The sintering temperature may be from about 1000°C to about 1600°C. The sintering time may be from about 5 minutes to about 10 hours.

Optionally, the metal foil or wire after the deoxidation treatment(s) can be subjected to acid leaching (eg HNO3) followed by a water rinse followed by drying.

Optionally, the oxidation treatment(s) and deoxidation treatment(s) may be performed without performing any annealing between the oxidation treatment and the deoxidation treatment.

Optionally, to form the capacitor anode of the present invention, the metal foil can be anodized in an electrolyte to form a dielectric oxide film or layer on the metal foil.

The capacitor anode of the present invention may have a current leakage of 10 nA/uFV or less. Such leakage may be, for example, 5 nA/uFV or less or 1 nA/uFV or less, about 0.1 nA/uFV to about 10 nA/uFV, or about 0.1 nA/uFV to about 5 nA/uFV, or about 0.1 nA/uFV uFV to about 1 nA/uFV.

The invention will become more apparent by the following examples which are intended to illustrate the invention.

Example

Example 1

In this example, porous metal foils and wires were prepared according to the present invention.

A commercially available, starting tantalum foil having a thickness of 0.07 mm manufactured by Global Advanced Metals, KK was used. This foil was cut to dimensions such that each piece of foil was 10 mm wide and 50 mm long. The tantalum foil was then _{acid leached in 30% HNO 3} , rinsed with deionized water and then dried.

Further, a starting tantalum wire having a diameter of 0.5 mm was cut to a length of 350 mm, wound into a spring shape, and then rinsed with acetone and dried. These starting capacitor grade tantalum wires were manufactured by Global Advanced Metals USA.

Several pieces of tantalum foil were used in the experiment, and wire pieces of different diameters were used in the experiment. A portion of the tantalum foil and some of the tantalum wire were subjected to chemical oxidation in a pre-molten KOH bath at approximately 500° C. for 5 minutes, rinsed with deionized water, and dried. This process is identified as "DGS" in the table.

All samples were then placed in a ceramic bowl and subjected to one of the treatments described below:

a) at 550° C. for 30 minutes

b) at 600° C. for 30 minutes

c) at 550° C. for 120 minutes

d) at 570°C for 120 minutes or

e) No air calcination at all.

In addition, some of the samples were then optionally vacuum annealed at 1400° C. for 20 minutes.

After that, all samples were subjected to deoxidation treatment including the use of magnesium chips. Specifically, 8 grams of magnesium chips were placed on the bottom of a tantalum box with dimensions 100 mm long, 60 mm wide and 25 mm high, and samples of tantalum foil and tantalum wire were placed on the magnesium chips, covered with a lid, and 750° C. or 980°C for approximately a total of 5 hours. An argon atmosphere was used during some of these times. After cooling, air passivation was performed through repeated cycles of vacuum pumping and air introduction.

Thereafter, the material subjected to deoxidation was _{acid leached using HNO 3} (60% concentration). The material was then rinsed with deionized water and dried. This deoxidation treatment was repeated twice using the same conditions.

For anode formation, a 60 mm long 0.5 mm diameter wire was welded to the specimen, and the tantalum foil and wire were subjected to vacuum sintering at 1200° C. for 20 minutes.

_{For anode formation, a 20 volt formation containing 0.1 vol% H 3} PO ₄ for 120 minutes at 60° C. was used, where the current density for the target Vf was 20 μA/mm ² . After that, electrical properties were measured.

Electrical measurements in liquid electrolyte were performed using a bias of 120 Hz and 1.5 volts at 25 °C in _{30 vol % H 2} SO _{4 for capacitance and 25 °C in 10 vol % H 3} PO ₄ for DC leakage. was performed using 14 volts with a 3 min charge.

The experimental results are presented in the table below.

According to the visual observation, in view of the electrical properties as indicated above, a porous structure was formed at least directly on the surface of the foil and wire by the use of the oxidation and deoxidation treatment of the present invention. In this example, a thin anode material with a thickness of less than 0.1 mm was obtained, and this anode had sufficient capacitance and DC leakage characteristics to be commercially viable, especially for use in small devices.

The present invention includes the following aspects/embodiments/features in any order and/or in any combination:

1. A porous metal foil or wire having a thickness and an outer surface, wherein the porous metal foil or wire a) a tantalum foil having a nominal thickness of 0.2 mm or less or a diameter of about 0.05 mm to about 1.0 mm, and b) A porous metal foil or wire comprising pores in at least said outer surface.

2. The porous metal foil or wire of any of the aforementioned or hereinafter described embodiments/features/aspects, wherein said nominal thickness is from 0.01 mm to 0.2 mm.

3. The porous metal foil or wire of any of the aforementioned or hereinafter described embodiments/features/aspects, wherein said diameter is between 0.05 mm and 0.5 mm.

4. The porous metal foil or wire of any of the aforementioned or hereinafter described embodiments/features/aspects, wherein said nominal thickness is from 0.02 mm to 0.18 mm.

5. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein the nominal thickness is between 0.03 mm and 0.18 mm.

6. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein the porous metal foil or wire has a purity level of at least 99.9% Ta.

7. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein the porous metal foil or wire has a purity level of at least 99.9% Ta and an amount of carbon less than 200 ppm.

8. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein the porous metal foil or wire has a purity level of at least 99.9% Ta and an amount of carbon less than 100 ppm.

9. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein the porous metal foil or wire has a purity level of at least 99.9% Ta and an amount of carbon from about 5 ppm to about 100 ppm.

10. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein the etched particulate exposed surface has an average particle size of from about 5 nm to about 500 nm.

11. The porous metal foil or wire of any of the aforementioned or hereinafter described embodiments/features/aspects, wherein the etched particulate exposed surface has an average particle size of from about 50 nm to about 200 nm.

12. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein said pores are further present at a level of at least 5 micrometers below said outer surface.

13. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein said pores are further present at a level of at least 10 micrometers below said outer surface.

14. The porous metal foil or wire of any of the preceding or hereinafter described embodiments/features/aspects, wherein said pores are further present at a level of at least 50 micrometers below said outer surface.

15. The porous metal of any of the preceding or hereinafter described embodiments/features/aspects, wherein the metal foil has a length of 10 mm to 50 mm, a width of 5 mm to 25 mm, and a nominal thickness of 0.01 mm to 0.2 mm. foil or wire.

16. A capacitor anode comprising the porous metal foil of any preceding or hereinafter described embodiment/feature/aspect and a dielectric oxide film on the porous metal foil.

17. The capacitor anode of any of the preceding or hereinafter described embodiments/features/aspects, wherein the porous metal foil is a sintered porous metal foil.

18. A capacitor comprising the capacitor anode of any preceding or hereinafter described embodiment/feature/aspect.

19. a. subjecting the metal foil or wire to an oxidation treatment to form an oxide layer on the metal foil or wire;

b. subjecting the metal foil or wire of step a) to a deoxidation treatment to form pores at least on the surface of the metal foil or wire;

A method of forming a porous metal foil or wire of any preceding or hereinafter described embodiment/feature/aspect comprising:

20. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein step b) is repeated one or more times after step a).

21. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein step a) is repeated one or more times and step b) is repeated one or more times.

22. The method of any preceding or hereinafter described embodiment/feature/aspect, wherein the oxidation treatment comprises calcining the metal foil or wire in air at a temperature of at least 500° C. for at least 5 minutes.

23. Any of the aforementioned or hereinafter described embodiments/features, wherein the oxidation treatment comprises calcining the metal foil or wire in air at a temperature of from about 500° C. to about 650° C. for a time of from about 5 minutes to about 10 hours. /side method.

24. The method of any of the preceding or hereinafter described embodiments/features/aspects, further comprising vacuum sintering the metal foil or wire after step b).

25. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein the oxidation treatment comprises a chemical oxidation treatment.

26. Any aforementioned or hereinafter described embodiment/feature/aspect, wherein the deoxidation treatment comprises subjecting the metal foil or wire of step a) to an oxygen getter material at a temperature of at least 500° C. for at least 5 minutes. way of.

27. Any of the preceding, wherein the deoxidation treatment comprises subjecting the metal foil or wire of step a) to an oxygen getter material at a temperature of about 700° C. to about 1300° C. for a time of about 5 minutes to about 10 hours. A method of an embodiment/feature/aspect described above or described below.

28. The method of any of the preceding or hereinafter described embodiments/features/aspects, further comprising, after step b), subjecting the metal foil or wire to acid leaching followed by rinsing with water and then drying.

29. Any of the preceding or described practices further comprising, after step b), sintering the metal foil and then anodizing the metal foil in an electrolyte to form a dielectric oxide film on the metal foil to form a capacitor anode A method of an aspect/feature/aspect.

30. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein the oxidation treatment forms the oxide layer having a thickness of at least 5 micrometers.

31. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein the oxidation treatment forms the oxide layer having a thickness of at least 10 micrometers.

32. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein the oxidation treatment forms the oxide layer having a thickness of at least 50 micrometers.

33. The capacitor anode of any of the preceding or hereinafter described embodiments/features/aspects, wherein the capacitor anode has a current leakage of 10 nA/uFV or less.

34. The capacitor anode of any of the preceding or hereinafter described embodiments/features/aspects, wherein the capacitor anode has a current leakage of 0.1 nA/uFV to 1.0 nA/uFV.

35. The method of any of the preceding or hereinafter described embodiments/features/aspects, wherein the oxidation treatment and the deoxidation treatment are performed without performing any annealing therebetween.

The present invention may include any combination of these various features or embodiments as set forth in sentences and/or paragraphs above and/or below. Any combination of features disclosed herein is considered part of the invention and no limitations are intended as to the features that can be combined.

Applicants specifically incorporate in this disclosure the entire contents of all cited references. Additionally, when an amount, concentration, or other value or parameter is provided as a range, preferred range, or list of larger and smaller preferred values, any greater than or equal to whether ranges are individually disclosed or not. It is to be understood that all ranges formed from any pair of a range limit or preferred value and any smaller range limit or preferred value are specifically disclosed. When a range of numerical values is recited herein, unless otherwise stated, the range is intended to include its endpoints, and all integers and fractions within the range. Where ranges are defined, they are not intended to be limited to the specific values recited.

Other embodiments of the invention will become apparent to those skilled in the art upon consideration of this specification and practice of the invention disclosed herein. The specification and examples are to be considered as illustrative only, and the true scope and spirit of the invention is intended to be expressed by the following claims and their equivalents.

Claims (35)

A porous metal foil or wire having a thickness and an outer surface, wherein the porous metal foil or wire has a) a tantalum foil having a nominal thickness of 0.2 mm or less or a diameter of about 0.05 mm to about 1.0 mm, and b) at least said A porous metal foil or wire containing pores on the outer surface. The porous metal foil or wire according to claim 1, wherein said nominal thickness is from 0.01 mm to 0.2 mm. The porous metal foil or wire according to claim 1, wherein the diameter is 0.05 mm to 0.5 mm. The porous metal foil or wire according to claim 1, wherein said nominal thickness is between 0.02 mm and 0.18 mm. The porous metal foil or wire according to claim 1, wherein said nominal thickness is between 0.03 mm and 0.18 mm. The porous metal foil or wire of claim 1 , wherein the porous metal foil or wire has a purity level of at least 99.9% Ta. The porous metal foil or wire of claim 1 , wherein the porous metal foil or wire has a purity level of at least 99.9% Ta and an amount of carbon less than 200 ppm. The porous metal foil or wire of claim 1 , wherein the porous metal foil or wire has a purity level of at least 99.9% Ta and an amount of carbon less than 100 ppm. The porous metal foil or wire of claim 1 , wherein the porous metal foil or wire has a purity level of at least 99.9% Ta and an amount of carbon from about 5 ppm to about 100 ppm. The porous metal foil or wire of claim 1 , wherein the outer surface comprises pores and an exposed particle-like surface, wherein the particle-like surface has an average major particle size of about 5 nm to about 500 nm. The porous metal foil or wire of claim 1 , wherein the outer surface comprises pores and an exposed particle-like surface, wherein the particle-like surface has an average major particle size of from about 50 nm to about 200 nm. The porous metal foil or wire of claim 1 , wherein said pores are further present at a level of at least 5 micrometers below said outer surface. The porous metal foil or wire of claim 1 , wherein said pores are further present at a level of at least 10 micrometers below said outer surface. The porous metal foil or wire of claim 1 , wherein said pores are further present at a level of at least 50 micrometers below said outer surface. The porous metal foil or wire of claim 1 , wherein the metal foil has a length of 10 mm to 50 mm, a width of 5 mm to 25 mm, and a nominal thickness of 0.01 mm to 0.2 mm. 16. A capacitor anode comprising the porous metal foil of any one of claims 1-15 and a dielectric oxide film on the porous metal foil. 17. The capacitor anode of claim 16, wherein said porous metal foil is a sintered porous metal foil. A capacitor comprising the capacitor anode of claim 16 or 17 . a. subjecting the metal foil or wire to an oxidation treatment to form an oxide layer on the metal foil or wire;
b. subjecting the metal foil or wire of step a) to a deoxidation treatment to form pores at least on the surface of the metal foil or wire;
A method of forming the porous metal foil or wire of claim 1 comprising a. 20. The method of claim 19, wherein step b) is repeated one or more times after step a). 20. The method of claim 19, wherein step a) is repeated one or more times and step b) is repeated one or more times. 20. The method of claim 19, wherein the oxidation treatment comprises calcining the metal foil or wire in air at a temperature of at least 500° C. for at least 5 minutes. 20. The method of claim 19, wherein the oxidation treatment comprises calcining the metal foil or wire in air at a temperature of about 500°C to about 650°C for a time of about 5 minutes to about 10 hours. 20. The method of claim 19, further comprising vacuum sintering the metal foil or wire after step b). 20. The method of claim 19, wherein said oxidation treatment comprises a chemical oxidation treatment. 20. The method of claim 19, wherein said deoxidation treatment comprises subjecting said metal foil or wire of step a) to an oxygen getter material at a temperature of at least 500[deg.] C. for at least 5 minutes. 20. The method of claim 19, wherein said deoxidation treatment comprises subjecting said metal foil or wire of step a) to an oxygen getter material at a temperature of about 700 °C to about 1300 °C for a time of about 5 minutes to about 10 hours. Way. 20. The method of claim 19, further comprising, after step b), subjecting said metal foil or wire to acid leaching followed by rinsing with water followed by drying. 20. The method of claim 19, further comprising, after step b), sintering the metal foil and then anodizing the metal foil in an electrolyte to form a dielectric oxide film on the metal foil to form a capacitor anode. 20. The method of claim 19, wherein said oxide layer is formed with a thickness of at least 5 micrometers by said oxidation treatment. 20. The method of claim 19, wherein said oxide layer having a thickness of at least 10 micrometers is formed by said oxidation treatment. 20. The method of claim 19, wherein said oxide layer is formed by said oxidation treatment having a thickness of at least 50 micrometers. 18. A capacitor anode according to claim 16 or 17, wherein said capacitor anode has a current leakage of 10 nA/uFV or less. 18. The capacitor anode of claim 16 or 17, wherein the capacitor anode has a current leakage of 0.1 nA/uFV to 1.0 nA/uFV. 33. The method according to any one of claims 19 to 32, wherein said oxidation treatment and said deoxidation treatment are performed without performing any annealing therebetween.

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